The recent removal of cabooses from the end of freight trains has generated a need for equipment which is capable of sensing and monitoring the brake line pressure and which is capable of confirming the presence of the last car. In practice, the equipment includes the electronics, radio transmitter, pressure transducer, and battery which are all housed within an appropriate protective casing. It has been found that the ideal equipment mounting location for the casing is on the open coupler of the last car, since the "glad-hand" of the coupling hose is readily available for measuring the brake line pressure. In addition, the last coupler location is obviously the end-of-train, and the body of the last car provides some protection against the elements and environment. However, the shape and bulkiness of the railroad car couplers makes it difficult to suitably mount the end-of-train equipment casing. Further, the equipment is exposed to the extreme shock and vibrations of the railroading milieu. Moreover, the equipment is repeatedly mounted and removed from the railroad cars and, accordingly, it is necessary to provide a method of quickly and easily attaching and detaching the end-of-train apparatus.